That's an interesting historical narrative, but I guess I'm talking on a more basic and specific level. The description above talks about its origins in "battlefield" arts, for armed and armored warriors. Is the idea then that aikido is based on grappling optimized for people wearing armor? I've never worn samurai armor, but my hunch is that it'd compel some changes from standard aikido movement.

Furthermore, I don't remember ever seeing Ueshiba-sensei or his students demonstrate in armor, or even move in a manner that seemed particularly reminiscent of someone in armor.

It's an interesting theory, though. Unfortunately, it seems rather hard to test. (You'd need to host some grappling matches with sets of armor.) Does anyone have knowledge of armored fighting methods from koryu studies? What are they like, technically?